(1) Field of the Invention
The present invention relates generally to an apparatus for forming a continuous fabric web and, more particularly, to an apparatus for forming and finishing a continuous fabric web in a single operation and the product produced thereby.
(2) Description of the Prior Art
Warp knitting machines can produce large width continuous fabric webs at high speed. The fabric webs produced by such machines have many industrial applications but often are subsequently coated with another material, such as plastic, to produce a composite material. In this case, the fabric web acts as a substrate to give added strength and the plastic coating may be, for example, a print receptive coating for signage. However to improve the adherence of the coating, it is often desirable to pre-treat the fabric web with an intermediate coating before putting on the final plastic coating.
While warp knitting machines having widths greater than 72 inches are common and relatively inexpensive, finishing machines having widths greater than 72 inches become exponentially expensive. In addition, the costs associated with moving such wide rolls of fabric can add substantial cost per yard to the final material. Prior art attempts to integrate the fabric forming and finishing operations into a single operation have not been very successful. Specifically, it is very difficult to control the thickness of the coating operation unless the coating operation is continuous. However, by its nature, fabric forming must be stopped and started when defects, such as broken yarns, occur.
Thus, there remains a need for an apparatus for forming and finishing a continuous fabric web which can be done in a single operation while, at the same time, the thickness of the pre-coating on the continuous fabric web can be precisely controlled even during starts and stops.
The present invention is directed to an apparatus for forming and finishing a continuous fabric web in a single operation. The apparatus includes a fabric web forming station for forming a continuous fabric web and a finishing station downstream from the fabric web forming station for receiving the continuous fabric web from the fabric web forming station and for providing a finishing treatment to the continuous fabric web. In the preferred embodiment, the fabric web forming station is a warp knitting machine having a creel and a plurality of yarn packages for supplying yarn to the warp knitting machine.
In the preferred embodiment, the finishing station includes a substantially excess-free applicator which helps to prevent thick spots in the coated fabric web which may occur when a coating applicator is stopped and restarted. The applicator of the present invention includes a liquid coating supply; an elongated pan extending across the width of the fabric web for containing the liquid coating; and an elongated knurled roller positioned in the pan in direct contact with the liquid coating and in direct contact with the bottom surface of the fabric web, whereby the rotation of the knurled roller transfers a predetermined amount of the liquid coating to the fabric web.
The volume of the grooves in the knurled surface of the knurled roller is proportional to the predetermined amount of the liquid coating being transferred to the fabric web. The predetermined amount of the liquid coating being transferred to the fabric web is substantially equal to the desired liquid take-up of the fabric web, thereby eliminating the need for removing excess liquid take-up from the fabric web.
To further control the accuracy of the amount of liquid being transferred from the knurled roller to the continuous fabric web, the deflection of the knurled roller is minimized in several ways. First, the bulk density of the knurled roller is less than about 3 times greater than the density of the liquid coating, thereby providing buoyancy to support the weight of the knurled roller. In the preferred embodiment the knurled roller is formed substantially from aluminum; however, the knurled roller could be jacketed with a high-density outer sheath and a low-density inner core. Second, a level control maintains the amount of liquid in the elongated pan at a predetermined level. Third, a deflection compensator attached to the knurled roller.
The deflection compensator is attached to the knurled roller includes a frame located at least one end of the knurled roller, a journal extending outwardly from the knurled roller, a first bearing attached to the frame for receiving the journal, a second bearing located at the outermost end of the journal and a pneumatic cylinder linkage attached between the second bearing and the frame for providing a downward force to compensate for the deflection of the knurled roller.
In the preferred embodiment, the finishing station includes a curing station downstream from the applicator. The curing station may include both a drying station and a heat set station downstream from the drying station. In the preferred embodiment the drying station includes a heat drum having a temperature between about 180xc2x0 C. and 225xc2x0 C. to remove most of the moisture from the coated continuous fabric web but not to produce VOCs which occur during curing of the coating. Desirably, a temperature of about 212xc2x0 F. will optimize the amount of moisture removed from the coated continuous fabric, while minimizing shrinkage of the fabric. A hood is located above the drying station for removing moisture driven off from the fabric web by the drying station. The airflow velocity of the hood is greater than about 400 CFM/ft of the width of the continuous fabric web which aids in drying the coated continuous fabric web. However, since the vapors include little or no VOCs, this large amount of air does not need to be treated further before being discharged into the atmosphere.
In the preferred embodiment, the heat set station includes a low thermal mass heat source which quickly cools when turned off. This permits the finishing station to be stopped and started as needed without burning the coated continuous fabric web. The heat set station also includes a hood located above the heat set station for removing VOCs driven off from the fabric web by the heat set station. Unlike the drying station, the airflow velocity of the hood is less than about 100 CFM/ft of the width of the continuous fabric web. This is a much smaller amount of air to be treated before being discharged into the atmosphere and results in substantial cost savings. In the preferred embodiment, the heat set station further includes a tenter frame for heat setting the continuous fabric web to a predetermined width.
Also in the preferred embodiment of the present invention is an accumulator located between the fabric web forming station and the finishing station for providing a fabric web reserve between the fabric web forming station and the finishing station. The accumulator includes a frame extending across the width of the continuous fabric web, a pair of arms each having one end attached to the frame on opposite edges of the continuous fabric web, a biased roller attached between the other ends of the pair of rollers and extending across the width of the continuous fabric web and a control system for varying the speed of the finishing station in response to the position of the accumulator arms.
Accordingly, one aspect of the present invention is to provide an apparatus for forming and finishing a fabric web in a single operation. The apparatus includes: a fabric web forming station for forming a continuous fabric web; and a finishing station downstream from the fabric web forming station for receiving the continuous fabric web from the fabric web forming station and for providing a finishing treatment to the continuous fabric web.
Another aspect of the present invention is to provide a finishing station for finishing a continuous fabric web, the finishing station including an applicator. The applicator includes: a liquid coating supply; an elongated pan extending across the width of the fabric web for containing the liquid coating; and an elongated knurled roller positioned in the pan in direct contact with the liquid coating and in direct contact with the bottom surface of the fabric web, whereby the rotation of the knurled roller transfers a predetermined amount of the liquid coating to the fabric web.
Still another aspect of the present invention is to provide an apparatus for forming and finishing a fabric web in a single operation. The apparatus includes: a fabric web forming station for forming a continuous fabric web; a finishing station downstream from the fabric web forming station for receiving the continuous fabric web from the fabric web forming station and for providing a finishing treatment to the continuous fabric web, the finishing station including: an applicator having (i) a liquid coating supply; (ii) an elongated pan extending across the width of the fabric web for containing the liquid coating; and (iii) an elongated knurled roller positioned in the pan in direct contact with the liquid coating and in direct contact with the bottom surface of the fabric web, whereby the rotation of the knurled roller transfers a predetermined amount of the liquid coating to the fabric web; and an accumulator between the fabric web forming station and the finishing station for providing a fabric web reserve between the fabric web forming station and the finishing station.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment when considered with the drawings.